1. Field
This disclosure relates generally to clock circuits for use by a system, and more specifically, to a clock circuit that can switch from one clock to another clock for use by a system.
2. Related Art
Particularly in systems that use a battery, power conservation is a major concern. In the case of mobile phones, communication is wireless using radio frequency (RF) communication. For effective communication, a clock is required that is closely controlled which requires a phase locked loop (PLL). PLLs generally require significant power. On the other hand it is common for a mobile phone to have other functions that do not require the closely controlled clock and thus do not require a PLL. Thus a technique for saving power is to use the closely controlled clock only when it is required and use another clock for the other operations. Switching between clocks, however, may result in problems such as glitches and abrupt phase changes, for the system during the transition.
Thus there is a need for a clock transition that avoids or reduces problems that may occur due to the transition.